{"id":283082,"date":"2023-05-09T14:32:57","date_gmt":"2023-05-09T14:32:57","guid":{"rendered":"\/forum\/forums\/topic\/error-in-aqwa-time-domain-simulation\/"},"modified":"2023-05-09T14:32:57","modified_gmt":"2023-05-09T14:32:57","slug":"error-in-aqwa-time-domain-simulation","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/error-in-aqwa-time-domain-simulation\/","title":{"rendered":"Error in Aqwa time domain simulation"},"content":{"rendered":"

Hello everyone,<\/p>\n

I am practicing Aqwa using the student version. I ran the diffraction solver for a ship shaped model with forward speed of 10 knots. This is the first time I am running a simulation with forward speed, in any software. The solver completed successfully. Then I ran a time domain simulation for irregular wave response in 180 deg waves with a PM spectrum (Hs-3m, Tz-8s). I faced the following issues. Hoping someone would be patient enough to read through them.<\/p>\n

    \n
  1. Even though the simulation completed successfully, when I checked the Animation it showed that the vessel capsized after few time steps and the rest of the simulation was completed in this capsized position. I tried to solve this by deactivating the Y, RX and RZ freedoms. Of course the model did not capsize this time, but what am I missing here? Why did it capzise in a simulation in head seas? Also, this method revealed my next issue.<\/li>\n<\/ol>\n

        2. In the animation, the model is moving backwards even though the diffraction was run with a forward speed. Probably my understanding is wrong here. Does giving a forward speed actually simulate the vessel to move forward or it only solves the diffraction problem for the corresponding encounter frequencies? So, is the model moving backwards because of the steady drift in 180 deg waves?<\/p>\n

        3. I found a possible work around (suggested by someone) which is to define a Structure Force in the +ve X direction for the entire duration of the simulation (3 hrs). I ran the simulation this way and it seemed to be working (while later looking at the TIMERESPONSE.LIS file) until the solver aborted at 10206 sec. Please see the error messages in the attached image. It says the time step 0.1 sec is too big. What is the appropriate time step? Did the structure force cause any issue? Was it the right method anyway, to make the model move forward?<\/p>\n

     <\/p>\n

    \"\"<\/p>\n

    Thanks in advance.<\/p>\n","protected":false},"template":"","class_list":["post-283082","topic","type-topic","status-closed","hentry","topic-tag-aqwa-errors","topic-tag-time-domain"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["284480","183765"],"_bbp_author_ip":["23.220.96.180"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["2529"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["283082"],"_bbp_forum_id":["27792"],"_bbp_engagement":["183765","284480"],"_bbp_voice_count":["2"],"_bbp_reply_count":["11"],"_bbp_last_reply_id":["287587"],"_bbp_last_active_id":["287587"],"_bbp_last_active_time":["2023-06-07 15:45:43"]},"test":"vishnu-iitkgpgmail-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/283082","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/283082\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=283082"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}